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Abstract Realizing extreme fast charging (XFC) in lithium‐ion batteries for electric vehicles is still challenging due to the insufficient lithium‐ion transport kinetics, especially in the electrolyte. Herein, a novel high‐performance electrolyte (HPE) consisting of lithium bis(fluorosulfonyl)imide (LiFSI), lithium hexafluorophosphate (LiPF₆) and carbonates is proposed and tested in pilot‐scale, 2‐Ah pouch cells. Moreover, the origin of improved electrochemical performance is comprehensively studied via various characterizations, suggesting that the proposed HPE exhibits high ionic conductivity and excellent electrochemical stability at high charging rate of 6‐C. Therefore, the HPE‐based pouch cells deliver improved discharge specific capacity and excellent long‐term cyclability up to 1500 cycles under XFC conditions, which is superior to the conventional state‐of‐the‐art baseline electrolyte. 

Carbonate-based electrolytes are widely used in Li-ion batteries but are limited by a small operating temperature window and poor cycling with silicon-containing graphitic anodes. The lack of non-carbonate electrolyte alternatives such as ether-based electrolytes is due to undesired solvent co-intercalation that occurs with graphitic anodes. Here, we show that fluoroethers are the first class of ether solvents to intrinsically support reversible lithium-ion intercalation into graphite without solvent co-intercalation at conventional salt concentrations. In full cells using a graphite anode, they enable 10-fold higher energy densities compared to conventional ethers, and better thermal stability over carbonate electrolytes (operation up to 60 °C) by producing a robust solvent-derived solid electrolyte interphase (SEI). As single-solvent–single-salt electrolytes, they remarkably outperform carbonate electrolytes with fluoroethylene carbonate (FEC) and vinylene carbonate (VC) additives when cycled with graphite–silicon composite anodes. Our molecular design strategy opens a new class of electrolytes that can enable next generation Li-ion batteries with higher energy density and a wider working temperature window.